Eyewire inspection station

ABSTRACT

An eyewinder system 10 has stations 100-108 for straightening, bending, measuring and transporting a wire 11 to form an eyewire 109. A controller 120 controls each station. Using information from tension and length measuring stations 104, 105, the controller 120 can accurately operate the second bending station 107. The eyewire 109 is inspected for accurate bends by an inspection system 140 that compares the bends in the eyewire 109 to predetermined radii of curvature.

This is a division of application Ser. No. 08/175,086 filed on Dec. 29,1993, now U.S. Pat. No. 5,479,683.

BACKGROUND OF THE INVENTION

This invention relates in general to eye wear, and in particular, to amethod and apparatus for shaping wire frames for holding lenses.

Many eyeglass frames are made of metal. The metal forms the temples thatloop over a person's ears, metal is used to form the bridge between twolenses, and the lenses are held in bent metal frames called eyewires.Each wire has its main curvature termed the shape curve about theoptical axis of the lens which will fit into it. In order to conform tothe edge of the lens, whose surface is spherical, it has a secondarycurvature, termed the base curve.

In order to form eyewires, a wire is fed from a spool, straightened, andthen bent at sequential bending stations to impart the first or basecurve and the second or shape curve to the eyewire. In prior artsystems, curves are imparted to the wires using a series of rollers withmovable elements at the end of the bender. The movable elements at theend of the bender are displaceable against the wire. The greater thedisplacement of the bending roller against the wire, the more curvatureis imparted to the wire as it passes over the roller. However, it isonly possible to bend the wire in one axis at one station. That is,there is no currently available technique for simultaneously impartingboth the base curve and the shape curve to the wire.

As such, one of the problems associated with prior art techniques hasbeen the coordination of the first and second bending stations in orderto impart the shape curve to the wire that has been impressed with abase curve. In order to solve this problem, the prior art techniqueshave relied upon bending stations having relatively small rollers and bypositioning the bending stations as close as possible to one another. Assuch, with closely positioned bending stations and small rollers(perhaps as small as one-quarter inch) the wire is bent as though thebase and shape curves are simultaneously made at one point on the wire.In other words, the distance that the wire travels between the first andthe second bending station is effectively ignored.

Even with small bending rollers, there is nevertheless a finitedifferential in wire travel between the first and second bendingstations. This finite distance contributes to errors in bending suchthat many eyewires are rejected in manufacture. Such prior art systemshave not included on-line correction of bending to accommodatevariations in wire. It is well known that there are significantmetallurgical differences between the wire at one end of a spool and thewire at the other end. Thus, as wire is withdrawn from a spool andformed into eyewires, the wire material itself will vary from segment tosegment as it passes through the two bending stations. However, in suchprior art bending systems, there is no provision for monitoring andon-line altering the bending characteristics of the two bending stationsin order to accommodate changes in the wire.

Such prior art eyewinder systems, due to the close proximity of thefirst and second bending stations, introduce large, and undesirablestresses in the eyewires. The latter is due to the sharp radii ofcurvature of the small bending rollers as well as the near simultaneousbending in orthoganol directions imparted by the two stations. As such,the wires become unduly stressed and many fail to conform to acceptablemanufacturing specifications.

Still another disadvantage of prior art systems is that finishedeyewires are only inspected by a manual optical comparison of theeyewire to metal fixtures of the desired shape. Because such techniquesare time consuming, cumbersome and inaccurate, inspections areinfrequent and thereby result in poor quality control.

SUMMARY OF THE INVENTION

The inventive apparatus and method includes a series of stations thatare operated by a controller, preferably a computer which operates eachstation in accordance with an interactive control algorithm and feedbackinformation provided by each station. A spool feeds wire into astraightening station. After the straightening station the wire passesthrough a first transport station into the first bending station. At thefirst bending station, the first or base curve is bent into the wire. Asa result of the first bending station, the portion of the wire exitingthe first bending station acquires a serpentine configuration. The firstbending station is significantly spaced from the second bending station.Between the first and second bending stations are a tension control ortension measuring station, a length measuring station and a secondtransport station. The tension measuring station measures the tension inthe wire as the serpentine wire exits the first bending station. It isimportant to control tension in the wire so that the length of the wirecan be controlled. In the length measuring station, a pair of rollerswith a suitable encoder transmits information to the controller aboutthe length of wire passing through the measuring station. By maintaininga length and tension measurement of the wire, coupled with informationabout where the bends are made at the first bending station, a secondbending station downstream can accurately place the shape curves orsecond bends at the appropriate location on the wire, as required by thedesign.

Upon exiting the length measuring station, the wire enters a secondtransport station where the wire is positioned for entry into the secondbending station. At the second bending station, the wire is bent alongthe orthogonal axis to impart a shape curve to the wire. The shape curveis appropriately imposed upon the wire at each point along its path.Upon leaving the bending station, the wire passes through a double shearstation where the eyewire is separated from the rest of the length ofthe wire.

After the shearing station, the eyewire may be sent to an inspectionstation where images of the base curve and shape curve are analyzed todetermine the radius of curvature at any one of a number of points. Theradii measurements are then compared to predetermined, desired radii forthe given shape of the wire. In accordance with a predetermined criteriastored in the controller, the wire will either pass or fail inspectionand its variation from the desired shape will be indicated by a suitabledisplay. In addition, errors in the radii and length noted by theinspection station will be used by the controller to adjust the processin order to bring the final eyewire into close conformity to the desiredoverall three-dimensional shape.

As mentioned above, the system employs at least two transport stations.In the inventive system, each transport station includes a plurality ofpairs of opposed rollers that are uniformly driven using a flexible beltwhich has teeth on either side. Such transport systems provide a softtransport of the wire and thus reduce damage to the wire while moving itfrom one station to the next.

In the preferred embodiment of the invention, the first and secondbending stations may be spaced apart as far as eight inches. Bydisposing a tension measuring station and a length measuring stationbetween the two bending stations, the controller operates the secondbending station in accordance with the measured tension and length ofthe wire so that the second or shape curve is accurately imparted to thewire as it passes through the second bending station. The system is alsocapable of reversing the travel of the wire. In order to give the wiresufficient clearance for shearing, a certain portion of the wire needsto be straight as it leaves the second bending station. Again, themeasuring station helps achieve this desirable result in combinationwith the controller which operates each of the stations of the system.

At the shearing station, the wire is double sheared. That is, the wireis disposed between two fixed dies and a movable die punches out asegment of the wire disposed between the fixed die. As such, both endsof the wire are slightly burred in the same direction. The latter isadvantageous because the burrs in the wire are disposed toward the lensand do not extend outwardly and create a burr on the outside surface ofthe eyewire.

The inspection station has a rotatable stage for receiving an eyewire. Alens and prism arrangement are used to project orthogonal images of theeyewire onto a camera, preferably a charge couple device camera. Giventhe orthogonal image generation system, the inspection station generatesimages of the base curve of the wire as well as the shape curve of thewire. These raw data images are processed using image correctionalgorithms in the controller for generating a series of measurements ofthe radii of curvature at different points along the surface of theeyewire. These radii of curvature are measurements of the radii ofcurvature of the base curve as well as of the shape curve taken at anumber of points around the periphery of the eyewire. These radiimeasurements are compared to predetermined, desirable radii and radiitolerances for eyewires that will conform to manufacturingspecifications. To the extent that any one or more measured points varyfrom acceptable standards, such variation is indicated by a display,either a written or a visual display. This information is alsointegrated to provide a measurement of wire length. In addition, theangle a shearing is recorded.

Based on measured variations in the radii of curvature from the desiredradii and overall wire length, the controller will optimize theindividual stations in the apparatus to bring subsequent wires intocloser conformity to the desired radii of curvature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the eyewinder system;

FIG. 2 is a sectional schematic drawing of the straightener station;

FIGS. 3A and 3B are respectively sectional and top views of a transportstation;

FIG. 4A is a plan view of the first bending station;

FIG. 4B is the first side view of the first bending station;

FIG. 4C is the second side view of the first bending station;

FIG. 4D is an expanded schematic view of the tension measuring station;

FIG. 4E is an expanded schematic view of the measurement station;

FIG. 5 is a schematic view of the second bending station;

FIG. 6A is a schematic sectional view of the shearing station;

FIG. 6B is a schematic view of the results of a prior art shearingoperation;

FIG. 7A is a schematic view of the inspection station;

FIG. 7B is a plan view of the stage of the inspection station;

FIG. 7C is an expanded view of the image area of the inspection station.

DETAILED DESCRIPTION

With reference to FIG. 1, there is shown an eyewinder system 10. Thesystem 10 includes a plurality of stations 85, 100-108 that operate onwire 11 to form an eyewire 109. The eyewire 109 is inspected by aninspection station 140. All of the stations 100-108 and the inspectionstation 140 are operated by a controller 120. Controller 120 includes acomputer, or other suitable device having a central processing unitand/or a microprocessor, random access memory, and suitable input/outputlines 95, 110-119 for receiving information from the stations 100-108and inspection station 140 and for transmitting control signals to thestations 100-108 and inspection station 140.

Wire 11 which is to be formed into an eyewire 109 is drawn from astandard reel of wire on a spindle at station 100. The station 100 hassuitable braking well known in the art to prevent an overrun of the wire11 as the wire 11 is withdrawn from the station 100. Wire 11 then passesinto a straightening station 101 whose function is to remove kinks fromthe wire before passing it on to a first transport station 102. Thestraightener 101 is shown in further schematic detail in FIG. 2. Thewire 11 has a major axis (largest second moment of area) which isgenerally vertical during travel through the system 10. The minor axisof the wire is deemed orthogonal to the major axis. As wire is withdrawnfrom spool 11, the wire likely has bends or curves in it and needs to bestraightened.

The straightening station 101 has first and second straighteners 101.1and 101.2 Each straightener 101.1 and 101.2 comprises nine rollers. Thefunction of these rollers is to cause the wire to follow a serpentinepath through the straightener. In transiting this serpentine path, theserpent is alternately bent up, then down, then up and then down so thatthe wire exits each straightener 101.1, 101.2 in an unbent condition. Assuch, as the wire passes through straightener 101.1, any residualdeformation in the minor axis is lost since the rollers in thestraightener are sufficient to deform the wire beyond its elastic pointand into its plastic region first one way and then the other so thatresidual plastic strain in the wire is lost and it comes out straight.Thus, the first straightener 101.1 straightens the wire along its minoraxis and the straightener 101.2 straightens the wire along its majoraxis. Such straightening stations including first and secondstraighteners 101.1, 101.2 are well known in the prior art. In a typicalseven station straightener, the first pair of rollers are opposed toeach other and the last two rollers are opposed to each other. Thesefirst and last pairs of rollers' guide and control the wire through thestraightening station. Five intermediate rollers are arranged to causethe serpentine passage of the wire and to form the wire into its plasticdeformation region.

After the wire 11 leaves the straightening station 101 it enters a firsttransport station 102. First transport station 102 is further shown inFIGS. 3A, 3B. The transport station 102 comprises drive rollers 304 thatare arranged in four pair of opposed rollers. A belt 300 made offlexible material, such as rubber, has teeth 301 on both sides thereofand passes between the opposed pairs of drive rollers 304, past a springtensioned idler roller 303 and over a drive pulley 302. As such, thedrive rollers 304 are driven uniformly by the tooth belt 300. Since thefour pairs of opposed rollers 304 are driven by the flexible tooth belt300, there is little or no backlash between the belt 300 and the gearsof drive rollers 304. The latter provides a soft transport for the wire11 as the wire passes through the first transport station 102. As such,any disparity in rotation between the rollers and the gears will beabsorbed by the teeth of the belt 300 rather than be transferred to thewire 11 as is the case with the standard gear drives of the prior art.

With reference to FIG. 3B, it is seen that the drive pulleys 304 aredisposed on one side of the transport station 102. The rollers 304 areabout one inch wide and have a smooth, improved surface. Upper shafts307 connect the upper drive rollers 304 to a set of wire pulleys 310.Each upper wire pulley 310 has a groove 316 for accommodating a portionof the wire 11. Lower rollers 304 have shafts 306 that couple to lowerwire drive pulleys 312. These lower wire drive pulleys 312 also have agroove 318 for accommodating the wire 11. The upper shafts 307 arespring biased toward the fixed lower shafts 306. Thus, as the rollers304 turn in one direction, their motion is imparted via shafts 307 and306 to wire drive pulleys 310, 318. Those pulleys, maintained in contactwith the wire by the springs on shaft 307, advance the wire 11 throughthe transport station 102.

Upon exiting the first transport station 102, the wire 11 enters thefirst bending station 103. With particular reference to FIGS. 4A-4B, itwill be noted that the wire 11 passes through four pairs of rollers:rollers 401, 402 are input guide rollers, intermediate rollers 416, 417and exit rollers 403, 404 which feed the wire 11 into a shuttle 405.Rollers 416 and 417 control the vertical position of the wire. Shuttle405 is reciprocally movable to bring one of two bending rollers 406, 407into contact with the wire 11. Roller 407 will bend the wire in onedirection and roller 406 in the other to impart a serpentine shape towire 11 and impress upon it the base curve. Shuttle 405 is operated by aball screw 408 and nut 409 that is coupled to the surface 412 of shuttle405. The ball screw is turned by a ball screw motor (not shown) inresponse to control signals on control line 113. The rotation of screw408 imparts reciprocal motion to shuttle 405. The shuttle 405 issupported by a pair of bushings 460, 461 with hardened slides 463, 464.The rollers 401, 402 and 416, 417 are about one inch and have a smooth,ungrooved surface.

After exiting the first bending station 103, the wire 11 passes througha tension measuring station 104 and a length measuring station 105 priorto entering the second bending station 107. It is important to controlboth the tension and the length of the wire in order to control thesecond bending station 107. As such, if the wire is allowed to droop andlose tension, its length will change thereby rendering inaccurate thecurves impressed by second bending station 107. The tension measuringstation 104 as shown in FIG. 4D can comprise a tension sensor wheel 430that bears against wire 11. The tension sensed by wheel 430 istransmitted via transducer 432 over communication line 114 to controller120. With such information, the controller 120 can control the speed ofthe transport stations 102, 106 and other stations to maintain asuitable tension on wire 11. Of course, the tension could be maintainedcorrectly by other means, so that it would be necessary to measure thetension. For example, after shearing, the wire 11 could be reversed byoperating the first transport station and letting the second transportstation freewheel in order to take up any slack in the wire 11.

The linear distance between first bending station 103 and second bendingstation 107 is known. However, in order to impart the second bends towire 11, the serpentine shaped wire is measured before entering thesecond bending station 107. Measuring station 105 is shown in FIG. 4E.It measures the length of the wire passing through station 105. A pairof rollers 441, 442 bear against the wire 11. At least one roller 441has its shaft 443 equipped with a suitable rotational measurement systemincluding an encoder 444 that measures the rotation of shaft 443 andconverts that rotational motion into an electrical signal transmittedvia line 115 to controller 120. The electrical signal from transducer444 is representative of the length of wire passing between rollers 441,442. The controller 120 keeps track of the drive speed of the wire aswell as the time when the first bends were made by first bending station103. With that information, coupled with the distance measurement takenby station 105, controller 120 is capable of operating the secondbending station 107 in order to bend the wire about its major axis andimpart the shape curve to the wire at the appropriate positions thereon.

After wire 11 leaves measuring station 105 it passes through a locatorshuttle 85 before entering a second transport station 106. The locatorshuttle 85 is coupled to controller 120 via control line 95. The shuttle85 is similar in construction and operation to shuttle 405 at the outputof first bending station 103. The shuttle 85 has a pair of output guiderollers that receive the serpentine wire 11. The rollers of the shuttle85 are driven by a ball screw under control of the controller 120. Thecontrol line 95 carries control signals to the shuttle 85 so that itsrollers are moved by its ball screw to correctly position the serpentinewire 11 for entry into the second transport station 106. Transportstation 106 is similar in function, construction and operation to firsttransport station 102.

After leaving second transport station 106, the wire 11 enters thesecond bending station 107. The second bending station 107 is also shownschematically in FIG. 5. In a preferred embodiment, second bendingstation 107 comprises a three point bender including three rollers 501,502, 503. The vertical position of the third roller 501 is suitablycontrolled by controller 120 in order to impart the shape curve toeyewire 11. Such three point benders are well known to those skilled inthe art. As such, as wire 11 passes through second bending station 105,the roller 501 is operated under control of controller 120 to impart thesuitable bending to wire 11 that will give it the desired shape curve ofeyewinder 109. The controller 120, which knows the distance between themeasuring station 105 and the second bending station 107, accuratelycontrols the motion of bending roller 501 in order to impart the shapeto eyewire 109.

Upon leaving second bending station 107, the eyewinder 109 passes intothe shearing station 108. Shearing station 108 is a so-called doubleshearing station as shown in FIG. 6A. There, a pair of dies 602, 603spaced apart from each other receive a punch 601. Punch 601 removes asection 130 from the eyewire 109. It will be noted that the punch 601can, when dull, leave small burrs on the edges of the eyewire 109. Itwill be appreciated that these small burrs at the tips 610 are disposedon the inside surface of the eyewire 109. Such burrs on the outsidesurface are unacceptable to the consumer.

Another feature of the invention that is possible with the controller120 is horizontal shearing of wire 11. This is achieved by suitablyadjusting the roller 501 in second bending station 107 so that about oneinch of the eyewire 109 is left perfectly horizontal. That inch is fedout of the second bending station and into the shearing station 108.After the eyewire 109 is sheared, the entire wire 11 is moved in theopposite direction back into the second bending station 107 where thesevered portion of the wire 11 is now bent appropriately by roller 501to provide the next eyewire 109.

The inspection system 140 is shown in further detail in FIG. 7. It isnecessary to inspect the finished eyewire because the metallurgicalproperties of the wire 11 change from one roll to another and alsochange throughout the unrolling process. As such, there is more plasticdeformation of the wire at the end of the roll than at the beginning.Accordingly, it is expected that the metallurgical properties of thewire will vary slightly as the wire is withdrawn from the roll. Thepurpose of the inspection system 140 is periodically to inspect the wireto see if the individual stations 101-108 need to have their operationsaltered in accordance with changed conditions of the wire. Of course, ifdesired, every eyewire 109 may be inspected or selected eyewires of aseries, e.g., one of every ten may be inspected.

With reference to FIG. 7A, the eyewire 109 is placed on a glass stage710 that rotates about an axis. A prism 703 is located at the center ofthe stage. The function of the prism 703 is to allow light to traversethe stage parallel to the surface of the stage.

A camera 706 is disposed on one side of the stage. A light source 701with a diffusing screen 702 and a reflection 713 are disposed on theopposite side of the stage. The light from light source 701 casts animage of the eyewire 109 onto the camera 706. The prism 703 casts animage of the inside edge of the eyewire 109 onto the camera 706. Theimage area 711 of the camera 706 is best shown in FIG. 7B and asexpanded in FIG. 7C. The image 714 shows the width W of the wire and theimage 712 shows the thickness T of the wire. Light 704 from the stage710 is focused by lens 705 of camera 706.

As such, as the stage 710 turns, orthogonal images of the same locationof the eyewire are projected onto the camera 706. So, the camera sees animage of the major as well as the minor axis of the eyewire 109. Assuch, at least two dimensions of the eyewire are measured.

As the stage 710 is turned, its position is measured using an opticalencoder or other means not shown, that is coupled to the controller 120.The camera is also operated by controller 120 to select a predeterminednumber of images, something between 200 and 250 images of the peripheryof the wire. For each image, the radius of curvature of the wire at thatlocation is derived. It will be appreciated that the image area 711 isfixed. However, the image of the major and minor axis, 712, 713 willvary with the radius of curvature of the base curve and the shape curveof the eyewire 109. As such, the position of the projection of images,712, 713 in the image area 711 is generally dependent on the radius ofcurvature of the eyewire 109. The camera 706 is typically a chargecoupled device camera. Using data from the 200 to 250 measurements,together with the rotational information for the stage 710, it ispossible to measure the length of the wire as well as the curvature ofthe wire in the vertical plane and the horizontal plane. By measuringthe radius of curvature at a predetermined number of points, each ofthose points can be compared to calculated points of an eyewire of thedesired shape. Such comparison is carried out by controller 120.Controller 120 makes a point-by-point comparison of the 200 to 250locations measured by camera 106 with predetermined radii of curvaturein the horizontal and vertical plane. If the eyewire is within the rangeof tolerance, the controller indicates acceptability by transmitting asignal via output line 160 to display 161. The acceptability indicationmay take the form of a visual or a printed display 161. If controller120 determines that one or more radii of curvature are outside thespecification limits, then the signal 160 to display 161 will indicatewhich of the radii of curvature are outside the limits. In oneembodiment of the device, a visual display 161 will include a firstimage of an acceptable eyewire together with an overlay image of themeasured eyewire and an indication on the visual display of where themeasured image significantly deviates from the ideal image.

The controller 120 will also use the data obtained from the inspectionsystem 140 to alter the operation of the various stations 101-108 inorder to optimize the bending of the wire 11 to produce an eyewire 109in conformity with the desired three-dimensional shape.

Having thus described the preferred embodiment of the invention, thoseskilled in the art will appreciate that various modifications,additions, and changes may be made thereto without departing from thespirit and scope of the invention as set forth in the following claims.

What is claimed is:
 1. An inspection station for inspecting eyewireshaving a base curve and a shape curve comprising:a stage for receivingan eyewire; means for generating images of the eyewire along twodifferent axes; means for measuring radii of curvature at selectedpoints along the two axes; a controller for storing a predeterminednumber of values of radii of curvature for the selected points; andmeans for comparing the stored values of radii to the measured radii ofcurvature for the selected points.
 2. The inspection station of claim 1wherein the stage is transparent and the means for generating images ofthe eyewire comprise a camera disposed on one side of the stage, asource of light disposed on the opposite side of the stage forprojecting a first image of a portion of the eyewire onto the camera anda prism for receiving a second image of said portion of said eyewire andprojecting said second image onto said camera.
 3. The inspection stationof claim 2 wherein the first image is representative of the shape curveand the second image is representative of the base curve.
 4. Theinspection station of claim 3 further comprising means for rotating thestage to change the portion of eyewire projected onto the camera.
 5. Aninspection station for inspecting eyewires having a base curve and shapecurve comprising:a stage for receiving an eyewire; means for rotatingthe stage and the eyewire about a central axis; means for capturingplanar and elevation images of the eyewire at selected rotational anglesof the stage; means for storing data of predetermined characteristics ofan eyewire; and means for comparing the planar and elevation images tothe stored data in order to determine if the inspected eyewire is withina range of tolerance of the stored data.
 6. The inspection station ofclaim 5 wherein the predetermined characteristics include a stored imageof a desired eyewire and the inspection station further comprises avisual display comparing an image of the inspected eyewire to the imageof the desired eyewire.
 7. The inspection station of claim 6 wherein thestored data comprises data of the radii of curvature of the desiredeyewire and the length of the desired eyewire.